The present invention relates to the treatment of heavy brines. More particularly, the present invention relates to the use of permanganates in the removal of heavy metal contaminants from heavy halide brines.
Brines are used commonly in subterranean operations during a variety of applications, including completion and workover operations. Generally, these brines are aqueous solutions of salts, such as calcium chloride, calcium bromide, zinc bromide, or mixtures thereof. During completion and workover operations, it may be desirable for the brines to be solids free. Brines that contain an undesirable level of solids may be problematic due, inter alia, to the undesirable introduction of solids into the near well bore region. During use, these brines may become contaminated with certain heavy metals (e.g., iron), which may render them unusable for these subterranean operations. For instance, these heavy metal contaminants may precipitate as the oxide or hydroxide thereof when the brine contacts the formation or mixes with formation water, thereby possibly causing formation damage. Iron contamination also may react adversely with polymers and cause a crosslink effect that may damage formations. Iron contamination also may stabilize brine/crude emulsions, which may have a detrimental impact on production. Furthermore, such contamination also may occur prior to use in storage tanks, transport vessels, and the like.
To remove such heavy metal contaminants from brines, the insoluble heavy metal contaminants may be separated from the brine by mechanical means, such as centrifugation, filtration, or decantation. To aid in the separation, liquid chemicals, such as bromate, hydrogen peroxide, or flocculants, may be added to the contaminated brine. These conventional reclamation treatments, however, may be problematic. For instance, substantial density may be lost as a result, and it may be necessary to perform multiple treatments in sequence. Another problem is that the byproducts from the conventional reclamation treatments typically may have a very low filterability, which may result in loss of brine volume and a substantial amount of residual sludge in the storage tanks that may need to be cleaned and transported to a waste disposal site, which can involve significant expenses.